Question about fuel consumption for you motor boaters from a yotty

[wonkywinch]

Being local, I follow the Parker Adams channel and just saw a nice looking Princess V52 for sale. It's out of my league at half a mil but I was just curious how thirsty this sort of boat would be with it's two Caterpillar C12 715HP engines.

When I venture from the Hamble to Bembridge or Newtown, in a rib it always cost me around £70 in fuel (petrol) for the trip. I guess this sort of boat is eye watering? Do owners hedge their fuel purchases?

No connection to the boat or agent, just like what Setag do.

 

[Portofino]

I had a pair of MAN 700 hp so similar enough to give you an idea .

Cruising on the plane which it’s designed for you are looking at 180-200 L/hr .
It held 2200 L in three tanks .
The speed depends on the hull form , displacement and drag . Mine did 28 knots at 180 L /hr , or above 30 @ the 200L/hr
I tended to cruise at under 80 % load , never really exceeded it didn’t need to …..in the interest of engine longevity and sympathy. Which in the 10 yrs of ownership played out uneventfully .It had annual lub changes .

That V52 will be a lot slower with its 715 s for the same fuel burn .It’s got a bigger hull to drag .

How ever at displacement speed that drops to 40 -50 L/ hr just before it starts to build a draggy bow wave .
Sort of 8-9 knots ^ . They will do D speed but really not configured for this and arguably it’s not healthy for the engines in the long term as they can’t reach optimal heat .

 

[GEM43]

That very conveniently works out at about £10/nm then @ £1.40/L

 

[Alicatt]

I had a pair of MAN 700 hp so similar enough to give you an idea .

Cruising on the plane which it’s designed for you are looking at 180-200 L/hr .
It held 2200 L in three tanks .
The speed depends on the hull form , displacement and drag . Mine did 28 knots at 180 L /hr , or above 30 @ the 200L/hr
I tended to cruise at under 80 % load , never really exceeded it didn’t need to …..in the interest of engine longevity and sympathy. Which in the 10 yrs of ownership played out uneventfully .It had annual lub changes .

That V52 will be a lot slower with its 715 s for the same fuel burn .It’s got a bigger hull to drag .

How ever at displacement speed that drops to 40 -50 L/ hr just before it starts to build a draggy bow wave .
Sort of 8-9 knots ^ . They will do D speed but really not configured for this and arguably it’s not healthy for the engines in the long term as they can’t reach optimal heat .

So much that, at canal speeds with my boat it struggles to get temperature in the engines, I usually idle one in gear to keep the pumps in the gearbox working and use the other to drive the boat, that gets a bit of temp in the engine, then I swap over to do the same with the other engine.

The engines smoke after a while at low rpm, give them a good blast and they clear and run sweet, only problem it is about 2hours away where I can open the boat up.

 

[jfm]

Very rough cruising figures at 20 knots, planing:

50 foot - 7 litres/nm
60 foot - 9
75 foot - 18
95 foot - 32

The latter two categories above would have generators running 24/7 so that's 6 and 9 litres /hour respectively.

Figures are radically less at displacement speed. (Ref comments above, there may be some instances of older engines or bad thermostats that result in not reaching correct temperature, but in general a modern diesel engine with a working thermostat will reach full temperature even when the boat is run at D displacement speed indefinitely.)

No, owners don't hedge these fuel purchases but sometimes get quantity discounts in the latter wo categories above where you're buying say 6-10k litres in one hit (or perhaps 20k litres if you synch with a neighbour).

 

[wonkywinch]

Interesting, thank you guys.

 

[MapisM]

or perhaps 20k litres if you synch with a neighbour

I don't think one full tank lorry would be enough for the whole PV gang nowadays, with 2x65' plus 2x95' boats!

 

[MapisM]

When I venture from the Hamble to Bembridge or Newtown, it always cost me around £70 in fuel (petrol) for the trip.

Since you declare you're asking as a yotty, I suppose you're referring to an outboard on a sailboat - and a smallish one, if she doesn't have an inboard diesel.
If so, unless I got wrong my rough math by heart, you're burning petrol in the 2 L/Nm ballpark, probably at 7kts or so.
And frankly, THAT actually sounds eye watering, in proportion!
I mean, just to expand on what jfm said above, I used to own a 53' trawler displacing 35T and powered by 2x350hp diesel engines.
And I had to push her at at 8.5kts to burn 2 L/Nm, because at or below 8 she burned even less.

 

[wonkywinch]

Since you declare you're asking as a yotty, I suppose you're referring to an outboard on a sailboat - and a smallish one, if she doesn't have an inboard diesel.
If so, unless I got wrong my rough math by heart, you're burning petrol in the 2 L/Nm ballpark, probably at 7kts or so.
And frankly, THAT actually sounds eye watering, in proportion!
I mean, just to expand on what jfm said above, I used to own a 53' trawler displacing 35T and powered by 2x350hp diesel engines.
And I had to push her at at 8.5kts to burn 2 L/Nm, because at or below 8 she burned even less.

My fault Mapis. I meant when I use a rib (250 outboard). Our Beneteau 38 has a 29hp 3 cyl Yanmar that sips around 2.5 litres an hour doing 6kts. I mostly sail so the 130 litre tank is still around half full since last fill in Sept last year.

 

[MapisM]

Aha, gotcha, that makes sense.

 

[jrudge]

The honest position is that unless you are going long distances at planning speed fule is not your biggest cost.

Berthing takes that prize.

I would think that and average user dong some decent trips and local trips will use 2 to 3 tanks of diesel a season.

My boat ( squadron 58 ) has 2700 litre capacity and in the real world a full usable tank is about 2200 litres allowing for the fact you don't run it empty. So 6600 litres a season so ball park £10k.

In the scheme of berthing / maintenance / lift and anti foul / repairs and upgrades / insurance it is not really that much of a material cost accepting that £10k is £10k

 

[sap_2000]

Did a 400 nm delivery trip with a V52 From Oslo to Bergen. Good conditions so 99% was done at 26-27 knots.
I always reset the trip and calculate after filling up at each leg.
The V52 with D11 670s used 6,4 liter pr nautical mile on that trip. My friend did a delivery of a CAT powered V52 and the figures was similar...
Not too bad consumption actually. One of my favourite boats in this size and class.

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[Grith]

Only yesterday I was talking to my neighbour seeing him drag away his wake boat and be back an hour or so later.
I asked if he had a launching or motor problem?
No he just took it to the petrol station and spent $800 on petrol! For the weekends use!
We have just arrived back from an exploration cruise of the Gippsland Lakes in Victoria Australia for 4 weeks and despite motoring half the time used about $140 of fuel on the yacht and $470 in the car to drag our yacht there and back a combined several thousand kilometres.
Fuel costs and the boats as mentioned above are not for relatively modest income retirees!
PS with a115hp outboard we almost count as a motor boat.

 

[Alicatt]

With 2 145hp very old Perkins diseasels and a 37ft semi displacement hull we have put almost 400km on our boat since last September, dipping the tanks we have not used enough diesel to consider putting more in her yet. Most of our running has been exceedingly slow at 6knots with a little at 15knots, we are mostly constrained by the amount of wake coming off the boat as we are allowed a maximum of 30cm reaching the banks which equates to about 12km/h (6.4knt) while the class of boat we have has a speed limit of 18km/h (9.7knt)
We have used about 4" out of an 18" deep 454litre tank, or roughly 101litres which works out about for 2.2litres per nautical mile

 

[jrudge]

As jfm says above at displacement speed the fuel bill is fractions of when planning. Our 58 is some 300 ish miles on a tank at planning speed and circa 800/900 at displacement.

In a flat sea or with stabilisation and a modest sea displacement is a lovely way to travel if you have the time. In rougher weather it is horrendous !

 

[Wasp]

Being local, I follow the Parker Adams channel and just saw a nice looking Princess V52 for sale. It's out of my league at half a mil but I was just curious how thirsty this sort of boat would be with it's two Caterpillar C12 715HP engines.

When I venture from the Hamble to Bembridge or Newtown, in a rib it always cost me around £70 in fuel (petrol) for the trip. I guess this sort of boat is eye watering? Do owners hedge their fuel purchases?

No connection to the boat or agent, just like what Setag do.

I have just become the proud new owner of this boat which I bought through Solent Motor Yachts.

Having had twin 390hp Cat diesels on my previous boat (Azimut 42 Evo), it was one of the features of this particular V52 which appealed to me. In my experience they are seriously decent marine engines.

As jrudge correctly commented, fuel burn is expensive with any twin screw planing boat, but in context of the overall cost of ownership, it is not quite so material.

In reality, like a lot of other leisure (motor) boaters along the Hamble, we don't tend to embark on very many extended journeys.
And when zipping to and from the popular Solent destinations, the best part of an hour is spent at min. revs navigating the Hamble and the harbour/marina at the other end.

Nevertheless, I checked out several fuel burn reports for the model before buying her, one from Princess and others from more objective sources.

I have now taken her on three round trips under varying loads and conditions.
The fuel consumption readouts on the dash (if accurate!) are suggesting, for example, 32 gallons per hour @ 1750 RPM/ 21kts. (negligible set/wind/calm sea).
Which I make 0.76 statute miles per gallon, (1.32GPM)

This seems to tally closely to the official stats and- when run at slightly higher load- to SAP2000's numbers (I calculated circa 0.70 statute MPG @ 1950 RPM/26kts), Circa 1.42 GPM, albeit measured over a much shorter journey.

These figures are only approx 12% costlier than comparables for the 42 ft boat.

If you then throw in the consumption at idling speeds, if using the boat for trips around the Solent or perhaps coastal hopping, it's a little shy of 1 MPG, averaged.

Interestingly, the consumption curve appears to be quite gentle between 17500 RPM and 2200 RPM, only entering eye watering territory nearer WOT @ 2340 RPM.(35 + knts)

In summary, if cruising around 80% load and on the plane, the fuel consumption is manageable. Trouble is that these engines feel solid as a rock, sound as sweet as a nut and produce bundles of torque, so the real challenge is resisting the urge to open the hammers!

As a side comment, Setag carried out a full interior refit on her in 2022 and they really have made her look and feel like a new boat (and better than a standard production model).
I always wondered if the cost/benefit equation was a little stretched, but I'm now sold. Literally.

 

[Sticky Fingers]

Which I make 0.76 statute miles per gallon, (1.32GPM)

That’s 7 litres / Nm. Seems low to me.

 

[jrudge]

for a 52 foot boat seems about right my 58 is between 8 and 10 depending when I last got it cleaned and the sea state.

 

[Sticky Fingers]

I was basing this on my 460, she’s quite a bit smaller, lighter, and a lot less power, that’s 5-6 litres/Nm at fast cruise. Happy to be proved wrong!

 

[rafiki_]

I was basing this on my 460, she’s quite a bit smaller, lighter, and a lot less power, that’s 5-6Nm/L at fast cruise. Happy to be proved wrong!

5Nm/litre seems incredibly economical? Surely 5l/Nm? Rafiki uses 1 gallon/Nm. So 4.5 litre. She is significantly smaller and lighter than your Prinny.